Reverse operation safety circuit

ABSTRACT

A safety system for a riding lawn mower that prevents powered operation of a PTO driven implement while in reverse unless an override switch is “ON”. The override switch may be a sustained action two position switch and the PTO driven implement may be a lawn mower blade. In one embodiment, the override switch does not allow the engine to start if the override switch is on. In one embodiment, the override switch cooperates with an operator presence switch to prevent operation of the PTO driven implement when the override switch is on and the operator is not present.

FIELD OF THE INVENTION

The present invention relates generally to lawn and garden tractors andsimilar vehicles. In particular, the present invention relates to areverse operation safety circuit for such a vehicle.

BACKGROUND OF THE INVENTION

Lawn and garden tractors often have power take offs (PTOs) that driveimplements such as mower blades. Prior lawn and garden tractors withPTOs have included interlock circuits that prevent engagement of the PTOdriven implement when the vehicle is in reverse. Under certainconditions, operation of a PTO driven implement while the vehicle is inreverse is desirable. Various override systems have been proposed thatallow operation of a PTO driven implement in reverse. Many of theseoverride systems are difficult to operate.

Override systems have been developed that use a momentary overrideswitch that latches an override relay. The override relay is unlatchedwhen certain other conditions are met, like shifting out of reverse.

One proposed system uses a four-position ignition switch. The positionsare “Off,” “Run with override on,” “Run with override off,” and “Start.”In that system the user must turn the key to the start position to startthe engine, thus resetting the override on engine restart. The ignitionswitch spring returns the key from the “Start” position to the “Run withoverride off position,” requiring an additional intentional movement ofthe key by the user to select “Run with override on.”

SUMMARY OF THE INVENTION

The present invention concerns a safety system for a riding lawn mowerthat prevents powered operation of a PTO driven implement while inreverse unless an override switch is “ON”. The override switch may be asustained action two position switch and the PTO driven implement may bea lawn mower blade. One aspect of the present invention is that theoverride switch does not allow the engine to start if the overrideswitch is on. A second aspect of the present invention is that theoverride switch cooperates with an operator presence switch to preventoperation of the PTO driven implement when the override switch is on andthe operator is not present.

Embodiments of the invention are reverse operation control circuits fora lawn tractor having an engine and a PTO. One reverse operation controlcircuit includes a battery, a starter motor, an ignition switch, and anoverride switch. The ignition switch selectively energizes the startermotor with the battery to start the engine. The override switch allowsoperation of a PTO driven implement while the lawn tractor is in reversewhen an actuator of the override switch is in a first position andinhibits operation of the PTO driven implement while the lawn tractor isin reverse when the actuator of the override switch is in a secondposition. The override switch inhibits the ignition switch fromenergizing said starter motor with the battery when the actuator of theoverride switch is in the first position. Movement of the actuator ofthe override switch from the first position to the second positionallows the ignition switch to energize the starter motor with thebattery if other conditions are met. In one embodiment, an “ON” overrideswitch inhibits the ignition switch from energizing the starter motor byopening a path between the ignition switch and a starter solenoid.

One reverse operation control circuit includes an operator presenceswitch, such as a seat switch, and an override switch. The operatorpresence switch and the override switch prevent the PTO driven implementfrom operating when an operator is not present and the override switchis “ON.” The PTO driven implement can be prevented from operating byusing the state of the override switch to shut down the engine.

One reverse operation control circuit includes an operator presenceswitch, an additional safety switch, such as a PTO engagement switch, abrake/clutch switch and/or a reverse sense switch, and an overrideswitch. The additional safety switch is connected to the operatorpresence switch. The operator presence switch and the additional safetyswitch prevent the PTO driven implement from operating when theadditional safety switch is in a first state and an operator notpresent. The override switch and the operator presence switch bypass theadditional safety switch to prevent the PTO driven implement fromoperating when an operator is not present and the override switch is“ON” regardless of the state of the additional safety switch.

One reverse operation control circuit includes a magneto, an operatorpresence switch, an additional safety switch, and an override switch.The additional safety switch is connected to the operator presenceswitch. The operator presence switch and the additional safety switchprovide a path from the magneto to ground to prevent the engine fromoperating when the additional safety switch is in a first state and anoperator not present. The operator presence switch and the overrideswitch provide a path from the magneto to ground that bypasses theadditional safety. This prevents the engine from operating when anoperator is not present and the override switch is in the “ON” positionregardless of the state of the additional safety switch.

One reverse operation control circuit includes a starter motor, areverse sensing switch for sensing when the lawn tractor is in reverse,a PTO switch for sensing when a PTO driven implement is engaged, and amow in reverse override switch. The override switch has an actuator thatis movable between an “ON” position and an “OFF” position. The mow inreverse override switch prevents the starter motor from starting theengine when the actuator is in the “ON” position. In addition, thereverse sensing switch, the PTO switch, and the mow in reverse overrideswitch prevent the engine from operating when the lawn tractor is inreverse, the PTO is engaged, and the actuator is in the “OFF” position.

One reverse operation control circuit includes a magneto coupled to theengine, a battery, a solenoid, an ignition switch for selectivelycommunicating current flow from the battery to the solenoid to start theengine, a reverse sensing switch for sensing when the lawn tractor is inreverse, a PTO switch for sensing when a PTO driven implement isengaged, and a mow in reverse override switch. The override switch hasan actuator that is movable between an “ON” position and an “OFF”position. The mow in reverse override switch opens a path from thebattery to the solenoid to prevent the engine from starting when theactuator is in the “ON” position. Further, the reverse sensing switch,the PTO switch, and the mow in reverse override switch provide a pathfrom the magneto to ground to prevent the engine from operating when thelawn tractor is in reverse, the PTO driven implement is engaged, and theactuator is in the “OFF” position.

Additional features of the invention will become apparent and a fullerunderstanding will be obtained by reading the following detaileddescription in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a lawn and garden tractor equipped with areverse operation override switch and safety switches;

FIG. 2 is a schematic of a control circuit for a lawn and gardentractor;

FIG. 3 is a schematic of a control circuit for a lawn and gardentractor; and

FIG. 4 is a schematic of a control circuit for a lawn and gardentractor.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure concerns a safety system 10 for a riding lawntractor 12. The safety system 10 includes an override switch 14 thatallows operation of a PTO driven implement 16 while the lawn tractor isin reverse when an actuator 18 of the override switch is in a first or“override ON” position and inhibits operation of the PTO drivenimplement while the lawn tractor is in reverse when the actuator 18 ofthe override switch is in a second or “override OFF” position. Oneaspect of an exemplary system 10 is that the override switch must be inthe “override OFF” position to start the engine. A second aspect of thepresent invention is that the override switch 14 cooperates with anoperator presence switch 24 to prevent operation of the PTO drivenimplement 16 when the override switch is “ON” and the operator is notpresent.

FIG. 1 illustrates a lawn and garden tractor 12 equipped with the system10 that allows operation of a PTO driven implement 16 when the tractoris in reverse. In the illustrated embodiment, the PTO driven implement16 is a mower blade. It should be readily apparent that the system 10could be applied to other PTO driven implements. For example, the PTOdriven implement could be a snow thrower. In the exemplary embodiment,the system 10 comprises a plurality of switches. The system illustratedby FIG. 1 includes an override switch 14, an operator presence switch24, a reverse sensing switch 26, an ignition switch 28, a PTO switch 30,and an engagement switch 32. The illustrated override switch 14 is asustained action, multiple pole switch. The illustrated operatorpresence switch 24 is positioned below a seat 34 to sense the presenceof an operator on the seat. In the illustrated embodiment, a lever 27controls whether the lawn and garden tractor is in “Forward” or“Reverse.” An actuator 29 of the illustrated reverse sensing switch 26is in communication with the lever, such that the position of theactuator 29 indicates whether the lawn and garden tractor is in“Forward” or “Reverse.” Referring to FIG. 2, the illustrated ignitionswitch 28 is a key switch that selectively energizes a starter motor 36with voltage from a battery 38 to start the engine 41. In the exemplaryembodiment, the ignition switch 28 closes a path between the battery 38and a starter solenoid 40 to energize the starter motor 36 with thebattery 38. On some lawn and garden tractors, movement of an actuator 42of the PTO switch 30 between an “ON” position and an “OFF” positioncauses engagement and disengagement of the PTO driven implementrespectively. On these tractors, the PTO switch 30 is coupled to apowered actuator that engages and disengages the PTO driven implementbased on the position of the PTO switch actuator. On other lawn andgarden tractors, the PTO driven implement 16 is engaged and disengagedby a manual movement of a mechanical PTO engagement linkage. On thesetractors, the PTO switch actuator is moved by movement of the PTOengagement linkage and thereby senses engagement and disengagement ofthe PTO driven implement. The engagement switch 32 senses engagement ofa brake 44 and/or engagement of a drive transmission 46. In theillustrated embodiment, a single switch senses the position of a pedal47 that engages the brake and disengages the transmission 46 whendepressed. In another embodiment, separate switches sense engagement ofthe brake and the transmission.

In the exemplary embodiment, the safety system 10 includes a safe startcircuit 50 (FIG. 2) and a safe operation circuit 52 (52′) (FIGS. 3 and4). The safe start circuit 50 prevents starting of the engine 41 whenthe switches sense a potentially unsafe condition. The safe operationcircuit 52, shuts the engine down (and thereby the PTO driven implement)or the PTO driven implement itself down when the switches sense apotentially unsafe condition. In the illustrated embodiments, theswitches of the safe start circuit 50 may also be used in the safeoperation circuit 52 (52′). For example, the override switch is includedin both the safe start circuit and the safe operation circuit.

A schematic of one suitable safe start circuit 50 is illustrated by FIG.2. It should be readily apparent that this circuit could be modified orother circuits could be used to perform the same function as theillustrated circuit. The illustrated safe start circuit 50 includes thebattery 38, an ignition switch start pole 54, an override switch firstpole 56, a PTO switch first pole 58, an engagement switch first pole 60,a starter solenoid 40, and a starter motor 36. The ignition switch startpole 54 is closed when the ignition switch 28 is moved to a “Start”position. The override switch first pole 56 is open when the overrideswitch 14 is in the “ON” position and is closed when the override switchis in the “OFF” position. The PTO switch first pole 58 is open when thePTO driven implement is engaged and is closed when the PTO drivenimplement is not engaged. The engagement switch first pole 60 is openwhen the transmission is engaged and/or the brake is not engaged and isclosed when the transmission is not engaged and/or the brake is engaged.The starter solenoid 40 includes a coil 70 and a pole 72. The pole 72closes when current passes through the coil 70.

A first battery terminal 62 is connected to ground. A second batteryterminal 64, is connected in series with the ignition switch start pole54, the override switch first pole 56, the PTO switch first pole 58, theengagement switch first pole 60, and a solenoid coil 70, which isconnected to ground. The second battery terminal 64 is also connected tothe solenoid pole 72, which is connected to the starter motor.

When the override switch is in the “OFF” position, the PTO drivenimplement is not engaged, and the transmission is not engaged and/or thebrake is engaged, movement of the ignition switch 28 to a “Start”position provides a path to solenoid coil 70. In this state, thesolenoid coil 70 is energized and the solenoid pole 72 closes.Electricity passes from the battery through the solenoid pole 72 to thestarter motor to start the engine 41. This condition, under which thecircuit illustrated by FIG. 1 allows the mower to start is defined byLogic Equation 1.Safe Start=Override OFF AND PTO Off AND Brake On  LOGIC EQUATION 1

The terms in Logic Equation 1 have the following meanings:

Override Off—The actuator of the override switch is in the “Off”position.

PTO Off—The PTO driven implement is not engaged.

Brake On—The brake is On and/or the transmission is not engaged.

When the override switch is in the “ON” position, the PTO drivenimplement is engaged, and/or the transmission is engaged (the brake isnot engaged), a path is not provided to the solenoid coil 70. Movementof the ignition switch 28 to the “Start” position does not energize thesolenoid coil 70 to close the solenoid pole 72 and the engine does notstart.

A schematic of a safe operation circuit 52 of a first embodiment isillustrated by FIG. 3. In one embodiment, the system 10 includes thesafe start circuit 50 illustrated by FIG. 2 and the safe operationcircuit 52 illustrated by FIG. 3. It should be readily apparent thatthis circuit could be modified or other circuits could be used toperform the same function as the illustrated circuit. In the embodimentillustrated by FIG. 3, the engine 41 is not necessarily shut down if theoperator gets out of the seat and the override switch is left ON. Thesafe operation circuit 52 illustrated by FIG. 3 includes an engine 41having a magneto 75, an override switch second pole 76, a PTO switchsecond pole 78, an engagement switch second pole 80, a reverse senseswitch first pole 82, an operator presence switch first pole 84, and anoperator presence second pole 86. In the safe operation circuitillustrated by FIG. 3, a path from the magneto 75 to ground is providedwhen an unsafe condition is detected to shut the engine down. Shuttingthe engine down also has the effect of shutting down the PTO drivenimplement. For example, the reverse sensing switch, the PTO switch, andthe mow in reverse override switch prevent the engine from operatingwhen the lawn tractor is in reverse, the PTO is engaged, and theoverride switch is “OFF.”

In the embodiment illustrated by FIG. 3, the override switch second pole76 is closed when the override switch is in the “OFF” position and isopen when the override switch is in the “ON” position. The PTO switchsecond pole 78 is closed when the PTO driven implement is engaged and isopen when the PTO driven implement is not engaged. The engagement switchsecond pole 80 is closed when the transmission is engaged and/or thebrake is not engaged and is open when the transmission is not engagedand/or the brake is engaged. The reverse sense switch first pole 82 isclosed when the tractor is in reverse and is open when the tractor isnot in reverse. The operator presence switch first and second poles 84,86 are closed when the operator is not present and are open when theoperator is present.

Referring to FIG. 3, the magneto 75 is connected to the PTO switchsecond pole 78. Connected in parallel with the PTO switch second poleare the engagement switch second pole 80 and the operator presenceswitch first pole 84, which are connected in series. When closed, thereverse sense switch first pole 82 connected in series with the overrideswitch second pole 76 provide a first path 90 to ground from the magnetothrough either (1) the PTO switch second pole 78 or (2) the seriesconnected engagement switch second pole 80 and the operator presenceswitch first pole 84. A second path 92 to ground from the magnetothrough either (1) the PTO switch second pole 78 or (2) the seriesconnected engagement switch second pole 80 and the operator presenceswitch first pole 84 is provided by the seat switch second pole 86 whenclosed. A list of conditions under which the circuit illustrated by FIG.3 does not ground the magneto and therefore allows the mower to continueoperating is set forth in Logic Equation set 2. If none of the equationsof Logic Equation set 2 are satisfied, the circuit illustrated by FIG. 3grounds the magneto to shut down the engine. Statements 2A–2G are allequivalent statements of the same logic condition for safe operation.

$\begin{matrix}{\mspace{239mu}{{EQUATUION}\mspace{14mu}{SET}\mspace{14mu} 2}} & \; \\\begin{matrix}{{{Safe}\mspace{14mu}{Operation}} = {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{OR}\mspace{14mu}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)} \right\rbrack\mspace{14mu}{AND}}} \\{\left\{ \left\lbrack {{NOT}\left( {{In}\mspace{14mu}{Reverse}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{On}} \right)} \right\rbrack \right.} \\{\left. {{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right\}\mspace{11mu}}\end{matrix} & {2A} \\\begin{matrix}{\mspace{160mu}{= {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{{OR}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)}} \right\rbrack\mspace{14mu}{AND}}}} \\{\left\lbrack \left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{NOT}\mspace{14mu}{Blades}\mspace{14mu}{On}} \right) \right.} \\\left. {{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right\rbrack\end{matrix} & {2B} \\\begin{matrix}{\mspace{160mu}{= {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{OR}\mspace{14mu}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)} \right\rbrack\mspace{14mu}{AND}}}} \\{\left\lbrack \left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}} \right)\mspace{14mu} \right.} \\{\left. {{OR}\mspace{14mu}{Override}{\;\mspace{11mu}}{On}} \right\rbrack\mspace{14mu}}\end{matrix} & {2C} \\\begin{matrix}{\mspace{166mu}{= {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{OR}\mspace{14mu}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)} \right\rbrack\mspace{14mu}{AND}}}\;} \\{\left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{11mu}{Blades}\mspace{14mu}{Off}}\; \right.} \\{\left. {{OR}\mspace{14mu}{Override}{\;\mspace{11mu}}{On}} \right)\;}\end{matrix} & {2D} \\\begin{matrix}{\mspace{166mu}{= {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}}}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{11mu}{On}\mspace{14mu}{OR}} \\{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \\{{{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}}\mspace{14mu}} \\{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}\mspace{14mu}{OR}} \\{{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}}\;} \\{{{AND}\mspace{14mu}{Override}\mspace{14mu}{On}}\;}\end{matrix} & {2E} \\\begin{matrix}{\mspace{166mu}{= {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}}}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{14mu}{On}\mspace{14mu}{OR}} \\{{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}}\;}\end{matrix} & {2F} \\\begin{matrix}{\mspace{166mu}{= {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}\left( {{Brake}\mspace{14mu}{On}} \right.}}} \\{\left. {{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right)\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}} \\{\left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right)}\end{matrix} & {2G}\end{matrix}$

The terms in Equation set 2 have the following meanings:

In Seat—An operator is present on the tractor.

Blades Off—The PTO driven implement is not engaged.

Blades On—The PTO driven implement is engaged.

Brake On—The brake is on and/or the transmission is not engaged.

In Reverse—The tractor is in reverse.

Override On—The override switch is on.

A schematic of a safe operation circuit 52′ of a second embodiment isillustrated by FIG. 4. In a second embodiment, the system 10 includesthe safe start circuit 50 illustrated by FIG. 2 and the safe operationcircuit 52′ illustrated by FIG. 4. It should be readily apparent thatthis circuit could be modified or other circuits could be used toperform the same function as the illustrated circuit. In thisembodiment, the safe operation circuit 52′ shuts the engine down if theoperator gets out of the seat and the override switch is left on. Thisprevents one or more situations from occurring. For example, a firstoperator could turn the mow in reverse switch on and get off the mowerwhile leaving the mower running. A second operator that gets on therunning mower would not have actively turned the mow in reverse switchon and might have no idea that the mow in reverse switch is on.Similarly, an operator could turn the mow in reverse switch on and getoff the mower while leaving the mower running. The operator could getback on the mower after a period of time, having forgotten that she hadturned the mow in reverse switch on. In this embodiment, the overrideswitch is a three pole switch. The first pole is used in the safe startcircuit and second and third poles 100, 102 are used in the safeoperation circuit.

The safe operation circuit 52′ illustrated by FIG. 4 includes an engine41 having a magneto 75, an override switch second pole 100, an overrideswitch third pole 102, a PTO switch second pole 78, an engagement switchsecond pole 80, a reverse sense switch first pole 82, an operatorpresence switch first pole 84, and an operator presence switch secondpole 86. In the embodiment illustrated by FIG. 4, a path from themagneto 75 to ground is provided when an unsafe condition is detected toshut down the engine, and thereby shuts down the PTO driven implement.For example, the operator presence switch and the override switch stopthe engine from operating when the operator leaves the lawn tractor andthe override switch is “O N.” The override switch second pole 100 isclosed when the override switch is in the “OFF” position and is openwhen the override switch is in the “ON” position. The override switchthird pole 102 is open when the override switch is in the “OFF” positionand is closed when the override switch is in the “ON” position. The PTOswitch second pole 78 is closed when the PTO driven implement is engagedand is open when the PTO driven implement is not engaged. The engagementswitch second pole 80 is closed when the transmission is engaged and/orthe brake is not engaged and is open when the transmission is notengaged and/or the brake is engaged. The reverse sense switch first pole82 is closed when the tractor is in reverse and is open when the tractoris not in reverse. The operator presence switch first and second poles84, 86 are closed when the operator is not present and are open when theoperator is present.

Referring to FIG. 4, the magneto 75 is connected to the PTO switchsecond pole 78. Connected in parallel with the PTO switch second poleare the engagement switch second pole 80 and the operator presenceswitch first pole 84, which are connected in series. Connected inparallel with the engagement switch second pole 80 is the overrideswitch third pole 102. When closed, the reverse sense switch first pole82 connected in series with the override switch second pole 76 provide afirst path 90 to ground from the magneto through either (1) the PTOswitch second pole 78, (2) the series connected engagement switch secondpole 80 and the operator presence switch first pole 84, or (3) theoverride switch third pole 102 and the operator presence switch firstpole 84. A second path 92 to ground from the magneto through either (1)the PTO switch second pole 78, (2) the series connected engagementswitch second pole 80 and the operator presence switch first pole 84, or(3) the override switch third pole 102 and the operator presence switchfirst pole 84 is provided by the seat switch second pole 86 when closed.

In the circuit 52′ illustrated by FIG. 4, the operator presence switchand the override switch provide a path 104 from the magneto to groundthat bypasses the additional safety switches. This prevents the enginefrom operating when an operator is not present and the override switchis in the “ON” position regardless of the state of the other safetyswitches.

A list of conditions under which the circuit illustrated by FIG. 4 doesnot ground the magneto and therefore allows the mower to continueoperating is set forth in Logic Equation set 3. If none of the equationsof Logic Equation set 2 are satisfied, the circuit illustrated by FIG. 3grounds the magneto to shut down the engine and thereby disable the PTOdriven implement. Statements 3A–3J are all equivalent statements of thesame logic condition for safe operation.

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{{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{NOT}\mspace{14mu}{Blades}\mspace{14mu}{On}} \right) \right.} \\{\left. {{OR}\mspace{14mu}{Override}\mspace{11mu}{On}} \right\rbrack\mspace{14mu}{AND}\mspace{14mu}\left( {NOT} \right.} \\\left. {{Override}\mspace{14mu}{On}{\mspace{14mu}\;}{OR}\mspace{20mu}{In}\mspace{14mu}{Seat}} \right)\end{matrix} & {3B} \\\begin{matrix}{\mspace{160mu}{= {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{OR}\mspace{14mu}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)} \right\rbrack\mspace{14mu}{AND}}}} \\{\left\lbrack \left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{11mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}} \right) \right.} \\{{\left. {{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right\rbrack{\mspace{11mu}\;}{AND}}\mspace{14mu}} \\{\left( {{Oevrride}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right)}\end{matrix} & {3C} \\\begin{matrix}{\mspace{160mu}{= {\left\lbrack {{In}\mspace{14mu}{Seat}\mspace{14mu}{OR}\mspace{14mu}\left( {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)} \right\rbrack\mspace{14mu}{AND}}}} \\{\left\lbrack {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}}\mspace{14mu} \right.} \\{\left. {{Override}\mspace{14mu}{On}} \right)\mspace{14mu}{AND}\mspace{14mu}\left( {{Override}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right)}\end{matrix} & {3D} \\\begin{matrix}{\mspace{160mu}{= \left( {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}} \right.}} \\{{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}}\;} \\{{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{14mu}{On}\mspace{14mu}{OR}}\;} \\{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}\mspace{14mu}{AND}} \\{{{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}}\mspace{14mu}} \\{{{Brake}\mspace{14mu}{On}\mspace{14mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}}{\mspace{14mu}\;}} \\{\left. {{On}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{11mu}{On}} \right)\mspace{14mu}{AND}} \\{\left( {{Override}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right)}\end{matrix} & {3E} \\\begin{matrix}{\mspace{166mu}{= \left( {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}} \right.}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{14mu}{On}\mspace{14mu}{OR}} \\{\left. {{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \right)\mspace{14mu}{AND}} \\{\left( {{Override}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right)}\end{matrix} & {3F} \\\begin{matrix}{\mspace{160mu}{= {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{AND}}}} \\{{Override}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}} \\{{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}} \\{{{AND}\mspace{14mu}{Override}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}}\;} \\{{{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{11mu}{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}}\;} \\{{On}\mspace{14mu}{AND}\mspace{14mu}{Override}{\;\mspace{11mu}}{Off}\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \\{{AND}\mspace{14mu}{Override}{\;\mspace{11mu}}{On}\mspace{14mu}{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}} \\{{{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}\mspace{14mu}{AND}\mspace{11mu}{Override}\mspace{14mu}{Off}}\mspace{20mu}} \\{{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \\{{AND}\mspace{14mu}{In}\mspace{14mu}{Seat}}\end{matrix} & {3G} \\\begin{matrix}{\mspace{160mu}{= {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}}}\mspace{11mu}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}} \\{{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}{Override}\mspace{14mu}{On}\mspace{14mu}{OR}} \\{{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \\{{AND}\mspace{14mu}{Override}\mspace{14mu}{Off}}\end{matrix} & {3H} \\\begin{matrix}{\mspace{155mu}{= {{In}\mspace{14mu}{Seat}\mspace{14mu}{AND}\mspace{14mu}\left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}} \right.}}} \\{\left. {{Blades}\mspace{14mu}{Off}\mspace{14mu}{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right)\mspace{14mu}} \\{{OR}\mspace{14mu}{Blades}\mspace{14mu}{Off}\mspace{14mu}{AND}\mspace{14mu}{Brake}\mspace{14mu}{On}} \\{{AND}\mspace{14mu}{Override}{\;\mspace{11mu}}{Off}}\end{matrix} & {3I} \\\begin{matrix}{\mspace{155mu}{= {{Blades}\mspace{14mu}{Off}\mspace{14mu}{{AND}\mspace{14mu}\left\lbrack \left( {{Brake}\mspace{14mu}{On}\mspace{14mu}{AND}} \right. \right.}}}} \\{\left. {\left. {{Override}\mspace{11mu}{Off}} \right)\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \right\rbrack\mspace{14mu}{OR}\mspace{14mu}{In}\mspace{14mu}{Seat}} \\{{AND}\mspace{14mu}\left( {{NOT}\mspace{14mu}{In}\mspace{14mu}{Reverse}\mspace{14mu}{OR}\mspace{14mu}{Override}\mspace{14mu}{On}} \right)}\end{matrix} & {3J}\end{matrix}$

The terms in Equation set 2 have the following meanings:

In Seat—An operator is present on the tractor.

Blades Off—The PTO driven implement is not engaged.

Blades On—The PTO driven implement is engaged.

Brake On—The brake is on and/or the transmission is not engaged.

In Reverse—The tractor is in reverse.

Override On—The override switch is on.

In the exemplary embodiment, the override switch is marked with one ortwo visual indicators or icons that convey switch function to theoperator. For example, the switch actuator could indicate by itsposition, which of two states (mow in reverse or no mow in reverse) iscurrently selected. This is not possible with momentary overrideswitches. The illustrated mow in reverse switch is a sustained actionoverride switch that is independent from the ignition switch.

Although the present invention has been described with a degree ofparticularity, it is the intent that the invention include allmodifications and alterations falling within the spirit or scope of theappended claims.

1. A reverse operation control circuit for a lawn tractor having anengine, a battery, a starter motor and a PTO, comprising: a) an ignitionswitch for selectively energizing said starter motor with said batteryto start the engine; and b) an override switch that allows operation ofa PTO driven implement while the lawn tractor is in reverse when anactuator of the override switch is in a first position and inhibitsoperation of the PTO driven implement while the lawn tractor is inreverse when the actuator of the override switch is in a secondposition, said override switch inhibits said ignition switch fromenergizing said starter motor with said battery when said actuator ofthe override switch is in said first position.
 2. The reverse operationcontrol circuit of claim 1 wherein the PTO driven implement is a mowerblade.
 3. The reverse operation control circuit of claim 1 whereinmovement of said actuator of said override switch from said firstposition to said second position allows said ignition switch toselectively energize said starter motor with said battery.
 4. Thereverse operation control circuit of claim 1 wherein a path between saidignition switch and a starter solenoid is open when said actuator of theoverride switch is in said first position to inhibit said ignitionswitch from selectively energizing said starter motor with said battery.5. The reverse operation control circuit of claim 1 wherein the overrideswitch is a sustained action two position switch.
 6. The reverseoperation control circuit of claim 1 further comprising a PTO switchthat controls engagement of the PTO driven implement, the PTO switchinhibits said ignition switch from selectively energizing said startermotor with said battery when the PTO switch causes engagement of the PTOdriven implement.
 7. The reverse operation control circuit of claim 1further comprising a PTO switch that senses engagement of the PTO drivenimplement, the PTO switch inhibits said ignition switch from selectivelyenergizing said starter motor with said battery when the PTO switchsenses engagement of the PTO driven implement.
 8. The reverse operationcontrol circuit of claim 6 wherein a path between said ignition switchand a starter solenoid is open when the PTO switch senses engagement ofthe PTO driven implement to inhibit said ignition switch fromselectively energizing said starter motor with said battery.
 9. Thereverse operation control circuit of claim 7 wherein a path between saidignition switch and a starter solenoid is open when the PTO switchcauses engagement of the PTO driven implement to inhibit said ignitionswitch from selectively energizing said starter motor with said battery.10. The reverse operation control circuit of claim 1 further comprisingan engagement switch that senses engagement of a brake, the engagementswitch inhibits said ignition switch from selectively energizing saidstarter motor with said battery when the engagement switch does notsense engagement of the brake.
 11. The reverse operation control circuitof claim 1 further comprising an engagement switch that sensesengagement of a transmission, the engagement switch inhibits saidignition switch from selectively energizing said starter motor with saidbattery when the engagement switch senses engagement of thetransmission.
 12. The reverse operation control circuit of claim 10wherein a path between said ignition switch and a starter solenoid isopen when the engagement switch does not sense engagement of the braketo inhibit said ignition switch from selectively energizing said startermotor with said battery.
 13. The reverse operation control circuit ofclaim 11 wherein a path between said ignition switch and a startersolenoid is open when the engagement switch senses engagement of thetransmission to inhibit said ignition switch from selectively energizingsaid starter motor with said battery.
 14. A reverse operation controlcircuit for a lawn tractor having an engine, a starter motor forstarting the engine, and a PTO, comprising: a) a reverse sensing switchfor sensing when the lawn tractor is in reverse; b) a PTO switch forsensing when a PTO driven implement is engaged; and c) a mow in reverseoverride switch having an actuator that is movable between a firstposition and a second position, wherein said mow in reverse overrideswitch prevents the starter motor from starting the engine when theactuator is in the first position and wherein said reverse sensingswitch, said PTO switch, and said mow in reverse override switch preventsaid engine from operating when the lawn tractor is in reverse, the PTOis engaged, and the actuator is in the second position.
 15. The reverseoperation control circuit of claim 14 wherein the mow in reverseoverride switch is a two position sustained action switch.
 16. Thereverse operation control system of claim 14 wherein the mow in reverseoverride switch allows the starter motor to start the engine when theactuator is in the second position.
 17. The reverse operation controlsystem of claim 14 wherein movement of the override switch actuator tothe first position allows the engine to operate when the lawn tractor isin reverse, the PTO is engaged, and the actuator is in first position.18. A reverse operation control circuit for a lawn tractor having anengine and a PTO, comprising: a) a magneto coupled to the engine; b) abattery; c) a solenoid; d) an ignition switch for selectivelycommunicating current flow from the battery to the solenoid to start theengine; e) a reverse sensing switch for sensing when the lawn tractor isin reverse; f) a PTO switch for sensing when a PTO driven implement isengaged; g) a mow in reverse override switch having an actuator that ismovable between a first position and a second position, wherein said mowin reverse override switch opens a path from the battery to the solenoidto prevent the engine from starting when the actuator is in the firstposition and said reverse sensing switch, said PTO switch, and said mowin reverse override switch providing a path from said magneto to groundto prevent said engine from operating when the lawn tractor is inreverse, the PTO driven implement is engaged, and the actuator is in thesecond position.
 19. The reverse operation control circuit of claim 18wherein the mow in reverse override switch is a two position sustainedaction switch.
 20. The reverse operation control system of claim 18wherein the mow in reverse override switch closes a path from thebattery to the solenoid when the actuator is in the second position. 21.The reverse operation control system of claim 18 wherein said path fromsaid magneto to ground is open when the override switch actuator is inthe first position, allowing the engine to operate when the lawn tractoris in reverse, the PTO driven implement is engaged, and the actuator isin first position.
 22. The reverse operation control system of claim 18wherein said mow in reverse override switch includes first and secondpoles wherein said first pole opens the path from the battery to thesolenoid to prevent the engine from starting when the actuator is in thefirst position and the second pole closes the path from the magneto toground to prevent the engine from operating when the lawn tractor is inreverse, the PTO driven implement is engaged, and the actuator is in thesecond position.
 23. A method of controlling reverse operation of a lawntractor, comprising: a) allowing operation of a PTO driven implementwhile the lawn tractor is in reverse when an actuator of an overrideswitch is in a first position; b) inhibiting operation of the PTO drivenimplement while the lawn tractor is in reverse when the actuator of theoverride switch is in a second position; and c) inhibiting energizing ofa starter motor when the actuator of the override switch is in saidfirst position.
 24. The method of claim 23 wherein the PTO drivenimplement is a mower blade.
 25. The method of claim 23 furthercomprising moving the actuator of the override switch from said firstposition to said second position to allow energizing of the startermotor with the battery.
 26. A method of controlling reverse operation ofa lawn tractor, comprising: a) sensing when the lawn tractor is inreverse; b) sensing when a PTO driven implement is engaged; c)preventing a starter motor from starting a lawn tractor engine when anoverride switch actuator is in a first position; and d) preventing saidengine from operating when the lawn tractor is in reverse, the PTOdriven implement is engaged, and the actuator is in a second position.27. The method of claim 26 further comprising allowing the starter motorto start the engine when the override switch actuator is in the secondposition.
 28. The method of claim 26 further comprising allowing theengine to operate when the lawn tractor is in reverse, the PTO drivenimplement is engaged, and the actuator is in first position.